Abstract: In this paper，a new asymmetric watermarking technique is proposed based on discrete wavelet transform firstly，the SOBEL operator is utilized to extract feature point in lowfrequency components through wavelet transform，secondly the watermarking is encoded by publickey functions，at last，the watermarking is embedded into the feature point.The result of experiment has proved the arithmetic is robust and invisible.The MATLAB engineer and its tool box are utilized to encode in VC++.

Key words: wavelet transform, extracting the edge of image with SOBEL, based on content of image, asymmetric watermarking

摘要： 在小波变换的基础上，提出了一种基于图像内容的非对称数字水印。首先，利用SOBEL算子提取经过小波分解后的低频区域中的图像的边缘特征的系数，存储在一向量中，利用非线性函数对水印加密，并将水印嵌入图像的边缘系数中。实验结果表明该算法具有极强的鲁棒性和不可见性。在实验过程中，利用MATLAB的引擎，在VC++中实现调用MATLAB的工具箱，快捷的编写了简洁的原代码。

关键词: 小波变换, SOBEL算子提取边缘, 基于图像的内容, 非对称水印